Charles and Camilla have started to make public appearances together

In a speech she wrote with her father, Major Bruce Shand, she told delegates at the summit of the final days of her mother Rosalind Shand, who died aged 72 in 1994.

Her decision to speak publicly has been seen by some royal watchers as another step towards her goal of public acceptance as Prince Charles's companion.

She said: "My mother's GP was kind and sympathetic but he was able to do little to alleviate the terrible pain she was in.

"We watched in horror as she quite literally shrunk before our eyes.

"She lost eight inches in height and became so bent, she could not digest her food."

Suffering

After her mother died, Mrs Parker Bowles went along to the National Osteoporosis Society headquarters in Bath and was "extremely impressed" with their work so decided to offer her help.

Queen Rania of Jordan hosted the conference

She outlined to delegates the lack of scanning equipment to detect the illness, and the shortage of physiotherapists and special nurses.

"We have a long, long way to go but we must emphasise the important of spending more money on early diagnosis.

"This could help prevent the suffering my mother, grandmother and thousands of others worldwide have and had to endure."

Mrs Parker Bowles joined 13 other high-profile women to sign a declaration calling for more action by governments all over the world to help patients with the condition.

Weak

The international conference, hosted by Queen Rania of Jordan, was organised to put pressure on policymakers.

Linda Edwards, director of the National Osteoporosis Society, said: "The disease is now at the level of awareness globally that can no longer be ignored."

One in three women and one in 12 men over the age of 50 will develop osteoporosis.

The skeleton becomes so weak that the simplest knock or fall can snap a bone, particularly in the wrist, spine and hip.

Mrs Parker Bowles's grandmother, Sonia, died aged 88 from the condition.